The Centers for Disease Control and Prevention (CDC) estimates that approximately 76 million people suffer from foodborne illnesses and 5,000 die from these illnesses in the United States each year. While many foodborne illnesses may be caused by poor food handling and preparation, they may also be caused by eating contaminated or adulterated foods. To reduce the number of foodborne illnesses from contaminated and adulterated foods, manufacturers can recall food that poses a risk of illness or injury. The U.S. Department of Agriculture (USDA) and the Food and Drug Administration (FDA) documented more than 3,700 food recalls from the mid-1980s through 1999. The USDA identified 515 recalls of fresh and processed meat and poultry from calendar year 1984 through 1999. The FDA identified 3,248 recalls of other food from fiscal year 1986 through fiscal year 1999. The USDA and FDA indicate approximately 61 of these recalls were outbreaks of foodborne illnesses, and have identified at least five bacteria and two viruses responsible for the outbreaks: E. coli O157:H7, Staphyloccocus species (toxin related), Vibrio parahaemolyticus, Listeria monocytogenes, Salmonella species, Hepatitis virus type A, Norwalk or Norwalk-like viruses. Foods involved in recalls vary widely, but some of the more common ones include oysters, ground beef, sprouts/seeds, strawberries/strawberry products, unpasteurized fruit juices/ciders, cold cuts, hot dogs, chicken, and pork.
The General Accounting Office (GAO) noted that food industry officials indicated recalls have a significant economic impact on affected companies through lost sales and food retrieval costs. The extent of the impact depends on such factors as the amount and value of the food recalled, its location in the distribution process, and the severity of the health risk. In addition, following a recall, consumers may stop buying a company's products or switch to another company's brand for future purchases. In some cases, this impact may lead to a company going out of business, particularly if the company is marginally profitable or already experiencing other problems. For example, a well-known company, Hudson Foods, went out of business after recalling approximately 25 million pounds of ground beef patties.
Recalls may also have an economic impact on companies other than the one conducting the recall. For example, according to the Food Marketing Institute, retail supermarkets may experience a drop in sales if consumers avoid the recalled food and other products by the same manufacturer or even other brands of the recalled item. In addition, companies that use a recalled product as an ingredient can incur significant costs from a recall. For example, if a particular brand of pepperoni is recalled a company using that brand in its frozen pizzas may have to recall the pizzas. Although the pizza manufacturer would be reimbursed for the lost revenues and replacement costs, it may also experience a drop in future sales if consumers have a negative impression of the pizza because of the recall. Because of the economic impact of recalls, many food companies have determined it necessary to carry “recall insurance” to cover lost revenues and retrieval costs, although many in the food industry have determined it cost prohibitive, leaving them open to the losses. GAO Report to Congressional Requesters “Food Safety: Actions Needed by the USDA and FDA to Ensure that Companies Promptly Carry Out Recalls”, GAO/RCED-00-195, August 2000.
The food processing industry, in an effort to avoid such problems and reduce costs, carries out more than 144 million microbial tests costing five to ten dollars each. About twenty-four million of these tests are for detection of food pathogens based on biochemical profile analysis, immunogenic tests (such as enzyme linked immunosorbent assays or ELISA) and DNA/RNA probes. These tests are reliable, but most require two to seven days to complete because of the steps that are needed to resuscitate cells, increase cell numbers or amplify genetic material needed for detection. This time period is too long for real-time detection of contamination in a food plant and is sufficiently long for contaminated food to be formulated, processed, packaged, shipped, and purchased and eaten by the consumer. Current tests require at least several days to confirm presence of Listera monocytogenes, for example. The number of annual tests is only expected to increase due to heightened consumer concerns about food safety and the requirement of compulsory testing.
In general, diagnostic tools typically used for detecting or quantitating biological analytes rely on ligand-specific binding between a ligand and a receptor. Ligand/receptor binding pairs used commonly in diagnostics include antigen-antibody, hormone-receptor, drug-receptor, cell surface antigen-lectin, biotin-avidin, substrate/enzyme, and complementary nucleic acid strands. The analyte to be detected may be either a member of the binding pair; alternatively, the analyte may be a ligand analog that competes with the ligand for binding to the complement receptor.
A variety of devices for detecting ligand receptor interactions are known. The most basic of these are purely chemical/enzymatic assays in which the presence or amount of analyte is detected by measuring or quantitating a detectable reaction product, such as a detectable marker or reporter molecule or ligand. Ligand/receptor interactions can also be detected and quantitated by radiolabel assays.
Quantitative binding assays of this type involve two separate components: a reaction substrate, e.g., a solid-phase test strip and a separate reader or detector device, such as a scintillation counter or spectrophotometer. The substrate is generally unsuited to multiple assays, or to miniaturization, or for handling multiple analyte assays. Further, these methods typically don't operate in “real time” situations.
In recent years, there has been a merger of microelectronics and biological sciences to develop what are called “biochips.” The term “biochip” has been used in various contexts but can be defined as a “microfabricated device that is used for delivery, processing, and analysis of biological species (molecules, cells, etc.).” Such devices have been used, among other things, for the direct interrogation of the electric properties and behavior of cells and optical detection of DNA hybridizations using fluorescence signals in the commercially available “DNA-chips”. Prior art chips have used impedance spectroscopy or simple impedance to detect microorganismal presence. U.S. Patent Application to Gomez et al., Pub. No. 2003/0157587, Aug. 21, 2003. The Gomez et al. application, utilizes bioseparation techniques on a biochip to detect a microbiological entity. The Gomez et al. method however, requires utilization of fluid samples and, preferably, a purification process prior to injection of the fluid on the biochip. Additionally, these types of biochips are usually limited to a detection capability of one or two organisms per chip.
There is clearly a need in the art for faster contaminant detection capability to facilitate a quick, reliable answer to the food industry of the presence of contaminants at potentially multiple stages in the manufacturing or preparation process. Further, the process needs to be repeatably reliable. Additionally, it would be extremely desirable to avoid complicated processes such as preparing solutions of, for example, ground beef, in order to detect contaminants. Such solutions are only spot reliable and time consuming. Therefore, there is a great need in the art for a method and apparatus which will detect contaminants, preferably multiple types of contaminants, on food during the preparation process and potentially at multiple points in the preparation process, for the entire supply instead of for small samples, and without having to prepare a liquid solution of the food product.